# CVE-2026-44660: ujson: UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+

CVE-2026-44660 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-44660, released May 27, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-44660
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0042
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 27, 2026

## Description

UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | python-ujson opensuse-leap 16.0 | 5.10.0-160000.3.1 | [OPENSUSE-SU-2026:21518-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21518-1.md) | Aug 3, 2026 |
| Linux | python-ujson sles 15.6 | 1.35-150100.3.13.1 | [SUSE-SU-2026:3539-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-3539-1.md) | Aug 10, 2026 |
| Linux | python-ujson sles 15.7 | 1.35-150100.3.13.1 | [SUSE-SU-2026:3539-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-3539-1.md) | Aug 10, 2026 |
| Linux | python-ujson sles 16.0 | 5.10.0-160000.3.1 | [SUSE-SU-2026:23136-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23136-1.md) | Aug 3, 2026 |
| Linux | ujson Debian 14 | 5.13.0-1 | [DEBIAN-CVE-2026-44660](https://patchblox.com/security/data/fix/linux/debian-cve-2026-44660.md) | May 27, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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